Index: llvm/lib/Target/RISCV/RISCVInstrInfo.td
===================================================================
--- llvm/lib/Target/RISCV/RISCVInstrInfo.td
+++ llvm/lib/Target/RISCV/RISCVInstrInfo.td
@@ -885,6 +885,10 @@
   return MatchSLLIUW(N);
 }]>;
 
+def add_oneuse : PatFrag<(ops node:$A, node:$B), (add node:$A, node:$B), [{
+  return N->hasOneUse();
+}]>;
+
 /// Simple arithmetic operations
 
 def : PatGprGpr<add, ADD>;
@@ -1299,6 +1303,12 @@
           (ADDI (ADDI GPR:$rs1, (AddiPairImmB GPR:$rs2)),
                 (AddiPairImmA GPR:$rs2))>;
 
+let Predicates = [IsRV64] in {
+def : Pat<(sext_inreg (add_oneuse GPR:$rs1, (AddiPair GPR:$rs2)), i32),
+          (ADDIW (ADDIW GPR:$rs1, (AddiPairImmB GPR:$rs2)),
+                 (AddiPairImmA GPR:$rs2))>;
+}
+
 //===----------------------------------------------------------------------===//
 // Standard extensions
 //===----------------------------------------------------------------------===//
Index: llvm/test/CodeGen/RISCV/add-imm.ll
===================================================================
--- llvm/test/CodeGen/RISCV/add-imm.ll
+++ llvm/test/CodeGen/RISCV/add-imm.ll
@@ -159,14 +159,37 @@
 ;
 ; RV64I-LABEL: add32_sext_accept:
 ; RV64I:       # %bb.0:
-; RV64I-NEXT:    lui a1, 1
-; RV64I-NEXT:    addiw a1, a1, -1097
-; RV64I-NEXT:    addw a0, a0, a1
+; RV64I-NEXT:    addiw a0, a0, 1500
+; RV64I-NEXT:    addiw a0, a0, 1499
 ; RV64I-NEXT:    ret
   %1 = add i32 %a, 2999
   ret i32 %1
 }
 
+@gv0 = global i32 0, align 4
+define signext i32 @add32_sext_reject_on_rv64(i32 signext %a) nounwind {
+; RV32I-LABEL: add32_sext_reject_on_rv64:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    addi a0, a0, 1500
+; RV32I-NEXT:    addi a0, a0, 1500
+; RV32I-NEXT:    lui a1, %hi(gv0)
+; RV32I-NEXT:    sw a0, %lo(gv0)(a1)
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: add32_sext_reject_on_rv64:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    lui a1, 1
+; RV64I-NEXT:    addiw a1, a1, -1096
+; RV64I-NEXT:    add a2, a0, a1
+; RV64I-NEXT:    lui a3, %hi(gv0)
+; RV64I-NEXT:    addw a0, a0, a1
+; RV64I-NEXT:    sw a2, %lo(gv0)(a3)
+; RV64I-NEXT:    ret
+  %b = add nsw i32 %a, 3000
+  store i32 %b, i32* @gv0, align 4
+  ret i32 %b
+}
+
 define i64 @add64_accept(i64 %a) nounwind {
 ; RV32I-LABEL: add64_accept:
 ; RV32I:       # %bb.0: